Circuits for wave transmission



Sept. 1, 1925.

1,551,624 J. c. SCHELLENG V CIRCUITS FOE WAVE TRANSMISSION Filed Juneso, 1924 lnvemor: John C. fiche/leng,

' vent theproductionof spurious oscillations;

Patented Sept. 1, 1925.

UNITED. TA S 'LSSLtZA; PATENT orrlcs.

JOHN G. soIIEImENe, or Ens'r O A GE, NEW ERsEY, AssIGNoR- T0 WESTERNELEC- ,rRIc coMrAN INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OFNEW YORK.

' omcuITs EoR WAvE TRANSMISSION.

To all whom it may concern:

Be it known that I, JOHN C. SGHELLENG,

a citizen-,ofthe UnitedStates of America, residing at East Orange, inthe county of Essex and State of NewJersey, have ins,

vented certain new and useful Improvementsin Y Circuits for WaveTransmission, of which the following is a 'full, clear, con cise,andexact description.

This invention relates to the production,

modulation and transmission of electrical oscillations, and moreparticularly to the space current type."

productiono-f oscillations byde'vices of the.

an oscillatorof simple construction conven-.

'iently adjustable to generate oscillations of any one frequency withina given range, and tomaintainthe'power output close to the maximum valueat "any one frequency.

Other objects of the inv'ention'are to preto improve the efliciencyTa ndthepower factor of the space currentrfrom the oscilla tor device; toconnect" theanode of anoscillatorof the spacecurrent 'type through astopping condenser to a grounded variometer in an antenna circuit insuchla manner that-the antenna isinsulatedirom the v voltage of the,space cui'rent. source; and toprovi'de a simple circuit in which the Ifrequency fisfva-riedby means of one variable element and the" poweinadjustment is accomplished by means of another variable element; I j Ia, .1

Certain features of the present invention are improvements vupon themethods and apparatus disclosed in British Patent No.

156.159, and a theoretical consideration ofproblems encountered inapparatus of the kind referred to will be understood more clearly'uponreference to this patent. I

' In accordance with the present invention, an oscillator utilizing aspace current de vice is arranged for adjustment to produce any desiredfrequency within" a given range,

and is so constructed that the power-gem erated at any frequency isclose to the maximum value. A variometer -for changing the frequencyoffthe generated oscillations automatically adjusts thecouplingcontrolling the production oftheoscillations. By con; necting avariable capacity between" the anode and cathode of the space currentdevice, provision is made ;fior improvi n-g the tenna is insulated fromthe voltageof the. space current source.

:Other features and objects'of the invenphase relation of the oscillatorcircuits and e and cathode are both grounded'and the antion will be moreclearly understood from the following detaileddescription in connectionwith the appended drawing. One object of'the invention is to" providefminal connected to antenna 8. is provided with a stationary portion 9adjacent to the grounded terminal, and arotary portion 10,

variably coupled to portion 9 and connected in series therewith remotefrom'the greunded terminal. Inductance winding 11 is inductively coupledto; variometer7, and

is thus variably coupled to movable inductmice '10. minals of winding'11 lead, respectivelyfto cathode 2 and grid 4:, the grid connectionincluding the condenser and grid leak *resistance 12 of well knownconstruction. I

Cathode 2 is connected directly to the grounded terminal of variometer7, and is thus grounded; 'Anode 3 is directly con- Connections from thetwo ternected to any desired point 'lll inductance 9by adjustment of thevariable connection 13 to adjust the ratio of the step-upauto-transformer formed by the anodecathode conne'ctions to variometer 7and the antenna-ground connections thereto. Blocking condenser'14connects anode 3 to -in-' ductance 9 and prevents the application toinductance 9 andto' antenna- 8 of the voltage from spacecurrent source5."

The capacity between antenna 8 and ground, together with the inductanceof variometer 7 and reactance inthe associated circuits, form a tunedcircuit Whichis predominant in determining the frequency ofoscillations. regeneratively produced by virtue of the coupling betweenvariometer 7 between18 and ground on the other.

' Oscillations transmitted through variometer 7 induce similaroscillations in winding 11, the induced oscilla tions being transmittedto grid 4 in a manner well known in the art. The frequency of thegenerated oscillations is adjusted to any desired value within a.considerablerange of frequencies by rotation of inductance 10 to varythe inductance of variometer 7 and the tuning of the antenna. It will benoted that'variation of the inductance of variometer '7 varies thecoupling betweenv variometer 7 in the anode-cathode circuit: and winding1-1 in, the grid-cathode circuit. The relation between th position ofinductance 10 and the position of inductance. 1-1 is so designed that,when the frequency is changed, the coupling between winding-'11 andvariometer 7 is adjusted to a value giving close tomaximum power outputfrom the oscillator and giving suitable stability to the operation ofthe oscillator.

A. sinall'variable. Capacity 15, connected between anode 3-andcathodeil, that is, between variable contact 13 and the groundedterminal of variometer 7, provides a path having-capacity reactance. inshunt to the lower portion ofinductance 9. This capacity is readjustedafter changing the frequency of the oscillations so that a stableadjustment-is obtained at properpower and cliic-iency withouttheproduction ofspurious oscillations. l hese spurious oscillations areordinarily of considerably higher frequency than those intended to begenerated for transmission to the. antenna. Capacity 1.5, apparentlybecauseof its low im Jedance to oscillations. of parasiticfrequency andits high impedance to wavesintended to be gen: erated, andipossibly foretlierreasons, pro-- vides an-easy means for suppressing the parasiticoscillations. v

The frequency of the oscillation occurring does not ordinarily differvery much from. one of the two resonant frequencies-otthe coupledcircuits formed by antenna 8, coil 16-, and the variometer-T on the onehand, and by capacity 15 and the section of-coilf) Ordinarily thecoupling between Hand? is made to be. of such phase as to produce thelower of these two frequencies, which is-somewhat lessithan thatof theantenna circuit alonea Condenser-15, by virtue of itscapacity reactance, may be adjusted-sothat the phase angle of'the load into whichthe tube .isde-: livering power is substantially Zero-.whileat the sametime all the other conditions necessary for-the production of stableoscillations are satisfied bythe circuit. In this way both the poweroutput andefficiency of device 1 are maintainedat-satisfactory val usthroughout the entire frequency range.

Inductance 16 is a, loading coil-:i'n the anand winding 11;.

tenna circuit which ordinarily has a fined value, being altered onlywhena general shift in the frequency range is required or when the antennais changed.

For the purpose of modulating oscillaions in accordance with telephonesignals, telephone. transmitter 17 is coupled by trans former 18 to theinput circuit 19 of amplifier 20, ofthewell known space current type,the anode circuit 21 of which is supplied with space current by source 5through choke coil 6, which functions to maintain a substantiallyconstant current-from source 5. Space current through tube is varied inwell known manner in accordance with speech-or sound waves fromtransmitter 17, and, inasmuch as the space current-through coil- 6 issubstantially constant, complemen: tary changes are produced in thespace current supplied to device; 1, thus causing modulation-of the.generated oscillations in accordance with the speechor soundwaves actingon transmitter 17, the modulated waves being radiated byantenna 8; Highfrequency choke coil 22 prevents the transmission of high frequencyoscillations from device 1 to device 20- and 6. It will be noted thatthe modulating.- system described utilizes the: well known principleofthe Heising constant current modulating system.

hen telegraplrsignalsare to be transmitted, switch 2v is connected; to.its.- upper position, establishing.connect-ion between battery 24- andbuzZer 2-j: Intermittent op eration of telegraph key 26causes-intermittent transmission to tube 20-ofwaves of the frequency of:buzzer "and producesa correspondingmodulation of. the oscillationsgenerated by device lVhat is claimed is 1. In an oscillator, a spacecurrentdevice having an anode, a cathode' and a control element, anantenna circuit having .an-inductance connectedat one of 'its terminalsto ground and to said cathode, a portion of said inductance beingvariably coupled to another-portion of-the inductance, means forcapacitatively coupling said-anode to a 'variable point in saiclcothrportion-of the inductance, an inductance conneetedbet'ween said controlelement and saidcathode and coupled to said other portionof the inductance, and a variable capacity connected between said anode andcathode:

2'. In an oscillator, a space-current device having. an anode, acathodeanda control element, an antenna circuit having an inductance connectedat one of its terminals togroundnand tosaid cathode, a portion of saidinductance remote fromthegrounded terminal 1 thereof being variablycoupled to a portion ofthe inductance adjacent the grounded terminal,means for oapacitatively coupling said-'anOde-toa variablevpointin theportion .ofsaid inductance adjacent said grounded terminal, aninductance connected between said control element and said cathode andcoupled to the portion of said antenna inductance remote from "thegrounded terminal, and a variable capacity connected between said anodeand cathode.

3. In an oscillator, a space current device having an anode, a cathodeand a control element, an antenna circuit having an inductance connectedat one of its terminals to ground and to said cathode, a portion of saidinductance remote from the grounded terminalthereof being variablycoupled to a portion of the inductance adjacent the groundedterminal,means for capacitatively coupling said anode to a variable point in thegrounded portion of said inductance, an inductance connected betweensaid control element and said cathode and coupled to the portion of saidantenna inductance remote from the grounded terminal, and meansconnected between one terminal of 7 said antenna inductance and thevariable point thereinfo'r reducing the'tendency for the oscillator togenerator parasitic oscilla tions and for increasing the power outputafter change of frequency. or

4. In an oscillator, a space current device having an anode, a cathodeand a control element, an antenna circuit having an in ductanceconnected at one of its terminals to ground and to said cathode, aportion ing said anode to said inductance and for varying the value ofthe inductance between said anode and cathode, a winding coupled to themovable portion of said antenna inductance, connectionsfrom said windingfor impressing oscillations on said control member', and meansassociated with said osto a portion of theinductance adjacent thegrounded terminal, means for capacitatively coupling said anode to avariable point in the grounded portion of said inductance, an inductanceconnected between said control element and said cathode and coupled tothe portion of said antenna inductance remote from the grounded terminalwhereby oscillations 1 are generated in accordance with the tuning ofsaid antenna circuit, and means whereby the generated oscillations aremodulated in accordance with signal waves;

' "6. In an oscillator, a space current device having an anode, acathode and a control element, a variometer having one of its terminalsconnected to an antenna and its other terminal connected to ground andto said cathode, an inductance coupled to the movable portion of saidvariometer and having connections for impressing oscillations on saidcontrol member, means connecting said'anode to a variable point betweenthe terminals ofsaid variometer, and a variable capacity connectedbetween said point and one of the terminals of said variometer.

In witness whereof, I hereunto subscribe my name-this 25th day of 1924;a

JoHN*o.so ELLENG,

June, A. -D.,

